diff --git a/lib/iris/_concatenate.py b/lib/iris/_concatenate.py
index 90f2438742..841cecfd53 100644
--- a/lib/iris/_concatenate.py
+++ b/lib/iris/_concatenate.py
@@ -690,9 +690,9 @@ def __init__(self, cube: iris.cube.Cube) -> None:
         #
         # Collate the dimension coordinate metadata.
         #
-        for coord in self.dim_coords:
-            dims = cube.coord_dims(coord)
-            self.dim_metadata.append(_CoordMetaData(coord, dims))
+        for dim_coord in self.dim_coords:
+            dims = cube.coord_dims(dim_coord)
+            self.dim_metadata.append(_CoordMetaData(dim_coord, dims))
             self.dim_mapping.append(dims[0])
 
         #
@@ -709,13 +709,13 @@ def key_func(coord):
                 cube.coord_dims(coord),
             )
 
-        for coord in sorted(cube.aux_coords, key=key_func):
-            dims = cube.coord_dims(coord)
+        for aux_coord in sorted(cube.aux_coords, key=key_func):
+            dims = cube.coord_dims(aux_coord)
             if dims:
-                self.aux_metadata.append(_CoordMetaData(coord, dims))
-                self.aux_coords_and_dims.append(_CoordAndDims(coord, tuple(dims)))
+                self.aux_metadata.append(_CoordMetaData(aux_coord, dims))
+                self.aux_coords_and_dims.append(_CoordAndDims(aux_coord, tuple(dims)))
             else:
-                self.scalar_coords.append(coord)
+                self.scalar_coords.append(aux_coord)
 
         def meta_key_func(dm):
             return (dm.metadata, dm.cube_dims(cube))
diff --git a/lib/iris/coord_categorisation.py b/lib/iris/coord_categorisation.py
index 770f8327a1..12ad93a9c3 100644
--- a/lib/iris/coord_categorisation.py
+++ b/lib/iris/coord_categorisation.py
@@ -30,7 +30,7 @@
 def add_categorised_coord(
     cube: iris.cube.Cube,
     name: str,
-    from_coord: iris.coords.Coord | str,
+    from_coord: iris.coords.DimCoord | iris.coords.AuxCoord | str,
     category_function: Callable,
     units: str = "1",
 ) -> None:
@@ -41,18 +41,18 @@ def add_categorised_coord(
 
     Parameters
     ----------
-    cube : :class:`iris.cube.Cube`
+    cube :
         The cube containing 'from_coord'. The new coord will be added into it.
-    name : str
+    name :
         Name of the created coordinate.
-    from_coord : :class:`iris.coords.Coord` or str
+    from_coord :
         Coordinate in 'cube', or the name of one.
-    category_function : callable
+    category_function :
         Function(coordinate, value), returning a category value for a coordinate
         point-value. If ``value`` has a type hint :obj:`cftime.datetime`, the
         coordinate points are translated to :obj:`cftime.datetime` s before
         calling ``category_function``.
-    units : str, default="1"
+    units :
         Units of the category value, typically 'no_unit' or '1'.
     """
     # Interpret coord, if given as a name